adding jsf components in form dynamically

[Iv� Conte]

i'm trying to add/remove in a jsf form <h:imputForm> dynamically using ArrayList but not works. What's wrong with my code??
backingbean method:

#  public String add()  
#    {  
#       UsuarioEntity ue=  new UsuarioEntity("","",null,"");  
#       ue.setId(0);  
#      
#       formDinamico.add(ue);  
#         
#       return "formDinamico";  
#    }      

jsp

#  <c:forEach var="campos" items="${usuarioBean.formDinamico}">  
#       <tr>  
#       <td><h:inputText value="#{campos.login}"/></td>  
#       <td><h:inputText value="#{campos.email}"/></td>  
#       </tr>  
#       </c:forEach>  
#       <tr><h:commandLink action="#{usuarioBean.add}" value="ADD"/><td></td></tr>      

stack trace:

   1. SEVERE: Servlet.service() for servlet Faces Servlet threw exception  
   2. org.apache.jasper.el.JspPropertyNotFoundException: /formDinamico.jsp(21,6) '#{campos.login}' Target Unreachable, identifier 'campos' resolved to null